Fuel cells

ABSTRACT

A gas permeable substrate comprises a porous metallic plate having a plurality of pores which form openings in an uppers surface and/or a lower surface thereof, and particles filled in the pores. In the gas permeable substrate, at least one of the upper surface and the lower surface of the porous metallic plate is substantially smooth.

TECHNICAL FIELD

The present invention relates to a gas permeable substrate and a solidoxide fuel cell using the same. Specifically, the present inventionrelates to a lightweight and thin gas permeable substrate which isparticularly suitable for a substrate of a solid oxide fuel cell, and toa solid oxide fuel cell using the same.

BACKGROUND ART

In a device using a solid oxide fuel cell (hereinafter, referred to asSOFC), an oxygen sensor, and a functional membrane such as a hydrogenseparation membrane, a gas permeable substrate has hitherto been used.For example, sintered ceramics used as a supporting substrate functionsas a supporting member and a gas passage. However, in terms of securinggas permeability and strength of the substrate, it has been difficult toreduce the weight and thickness of the device.

From the viewpoint of reduction in weight and thickness, a metallicfilter has been proposed, which has a two layer structure of a wire meshsubstrate and sintered metal powder or the like coated thereon (seeJapanese Patent Application Laid-Open No. H7-60035).

Moreover, a metallic filter has been proposed, which is made by applyingpowder on a substrate obtained by pressing down the wire mesh. Thismetallic filter is used to filter various oils, gases, liquids, and thelike (See Japanese Patent Publication No. 3146387 and Japanese PatentApplication Laid-Open No. H8-229320). This filter is used with the poresize adjusted according to the size (particle size etc.) of an object tobe filtered.

As the SOFC using a gas permeable substrate, an SOFC has been proposed,in which power generating elements (fuel electrode, electrolyte, and airelectrode) are deposited on the porous metallic substrate by spraying(see Plasma Sprayed Thin-Film SOFC for Reduced Operating Temperature,Fuel Cells Bulletin, pp 597-600, 2000).

Moreover, a part for hydrogen separation has been proposed, which isconstructed by covering the gas permeable substrate with a film, foil,or sheet having a function of hydrogen separation. This part forhydrogen separation is used through gas to be separated, the gas beingpressurized in a thickness direction of the substrate.

DISCLOSURE OF THE INVENTION

However, in Japanese Patent Application Laid-Open No. H7-60035, sincethe wire mesh protrudes from the sintered metal powder layer, in otherwords, since the wire mesh is not buried in the sintered metal powderlayer, it is difficult to make the substrate thinner.

In the Japanese Patent Publication No. 3146837, the metallic filter isconstructed by pressing down the wire mesh. Accordingly, it isimpossible to obtain a flat surface of the substrate because of partwhere the wire mesh is protruded, and it is difficult to form a thinfilm thereon. In addition, since the powder layer is formed on the wiremesh, there has been a problem that the entire filter is made thick.

In the SOFC described in Fuel Cells Bulletin, a separate gas passage isprovided, since the substrate cannot be utilized as a gas passage. Thisis because the upper surface of the porous metallic substrate is finelyformed so that film forming by spraying becomes possible. Accordingly,the number of parts has been increased, and cell parts including acollector and the gas passage have been made thick. Therefore,miniaturization thereof has been difficult.

The part for hydrogen separation is used through the gas to beseparated, the gas being pressurized in the thickness direction of thesubstrate. In this case, when the part for hydrogen separation is usedonly for separating hydrogen, electrical conductivity is not required onthe porous substrate. However, when the part for hydrogen separation isused for the SOFC, electrical conductivity is required on the substratewith a collector function given. Moreover, in the SOFC, since the gasflows in a plane direction of the porous substrate, higher gaspermeability is required on the porous substrate.

The present invention has been accomplished to solve the above problem.It is an object of the present invention to provide a lightweight andthin gas permeable substrate which has high gas diffusion and has ahigh-contact rate and adhesion with a functional material, and toprovide a solid oxide fuel cell using the same.

The first aspect of the present invention provides a gas permeablesubstrate, comprising: a porous metallic plate having a plurality ofpores which form openings in an upper surface and/or a lower surfacethereof; and particles filled in the pores, wherein at least one of theupper surface and the lower surface of the porous metallic plate issubstantially smooth.

The second aspect of the present invention provides a solid oxide fuelcell, comprising: a gas permeable substrate having a porous metallicplate which includes a plurality of pores forming openings in an uppersurface and/or a lower surface thereof; and particles filled in thepores, wherein at least one of the upper and lower surfaces of theporous metallic plate are substantially smooth, and single cells arestacked, each single cell including power generating elements stacked onan upper surface and/or a lower surface of the gas permeable substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view showing a gas-permeablesubstrate of the present invention;

FIG. 2 is a schematic cross-sectional view showing the othergas-permeable substrate of the present invention;

FIG. 3 is a schematic cross-sectional view showing the othergas-permeable substrate of the present invention;

FIGS. 4A and 4B are plan views showing a gas-permeable substrate with aframe according to the present invention;

FIG. 5 is a schematic cross-sectional view showing a SOFC of the presentinvention;

FIG. 6 is a schematic cross-sectional view showing the other SOFC of thepresent invention;

FIG. 7 is a schematic cross-sectional view showing a gas-permeablesubstrate of an Example 3;

FIG. 8 is a schematic cross-sectional view showing a gas-permeablesubstrate of an Example 5;

FIG. 9 is a schematic cross-sectional view showing a gas-permeablesubstrate of a Comparative Example 1;

FIG. 10 is a SEM view showing a cross-section of a gas-permeablesubstrate of an Example 1; and

FIG. 11 is a SEM view showing a cross-section of a gas-permeablesubstrate of an Example 2.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be explained below withreference to the drawings, wherein like numbers are designated by likereference characters. For convenience of explanation, one side of theporous metallic plate or the like is described as an upper surface, andthe other side thereof is described as a lower surface. However, theseare equivalent elements, and a construction in which these elements aresubstituted for each other is included in the scope of the presentinvention.

First Embodiment

A gas permeable substrate of the present invention includes: a porousmetallic plate having a plurality of pores which form openings in theupper surface and/or the lower surface thereof; and particles filled inthe pores. The gas permeable substrate is characterized in that at leastone of the upper and lower surfaces of the porous metallic plate issubstantially smooth. Specific embodiments are shown in FIGS. 1 to 3. Asshown in FIG. 1, a gas permeable substrate 1 of the present inventionincludes a porous metallic plate 3 and a particle layer 7. The porousmetallic plate 3 includes a plurality of pores 5, and openings 5 a and 5b based on the pores 5 are formed on an upper surface 3 a and a lowersurface 3 b of the porous metallic plate 3. Particles are filled inthese pores 5 to form the particle layer 7 and the upper surface thereofis made smooth. The gas permeable substrate 1 of the present inventionis thus obtained.

With such a construction, the gas permeable substrate 1 becomeslightweight and thin, and functions as both a supporting member and agas passage. Moreover, an entire device using this gas permeablesubstrate 1 can be designed to be lightweight and small. Moreover, sincegas passes through holes within the particle layer 7, the gas can passthrough the substrate while being efficiently diffused. In terms of thepores 5 included in the porous metallic plate 3, each pore 5 ispreferably penetrated in the vertical direction, namely, in thethickness direction of the plate. However, it is sufficient if the pore5 is penetrated in the vertical direction by having an opening on onesurface and communicating with another pore within the metallic plate 3.

The gas permeable substrate 1 of the present invention is typicallymanufactured as follows. Slurry of the particles is applied to theporous metallic plate 3 by screen printing, green sheet method, dipping,or the like and baked in vacuum, inert atmosphere such as nitrogen orargon, or in reducing atmosphere such as hydrogen. At this time, apore-forming material or the like can be properly used in order toprovide holes in the particle layer 7.

Preferably, the particle layer 7 covers not less than 30% of the area inthe upper surface 3 a of the porous metallic plate 3 and/or not lessthan 30% of the area in the lower surface 3 b thereof. In other words,the construction is preferred in which the surface portion of the porousmetallic plate 3 is buried in the particles as shown in FIG. 2. Thisenables gas to be diffused over the entire surface of the porousmetallic plate 3 through the particle layer 7. When the covered area isless than 30%, the particle layer 7 is thin, and the strength of the gaspermeable substrate 1 is reduced. In the case where the metallic plate 3includes a function as a collector and the like, the function issometimes lowered since the contact area between the metallic plate 3and the particles is reduced with the contact area less than 30%.Specifically, the contact area between the metallic plate 3 and theparticles is reduced, and electrons may not be efficiently transferredbetween the particle layer 7 and the metallic plate 3.

The particles filled in the pores 5 and the particles covering the upperand lower surfaces 3 a and 3 b of the porous metallic plate 3 may be ofthe same material or different materials.

In the light of gas permeability and durability of the porous metallicplate, it is preferable that the particles constituting the particlelayer 7 are made of ceramics or a composite material of ceramics andmetal. Examples of the ceramics include NiO, CuO, Al₂O₃, TiO₂, ceriasolid solution, stabilized zirconia, lanthanum cobalt oxide, andlanthanum manganese oxide. Examples of the metal include nickel,nickel-boron alloy, platinum, platinum-lead alloy, and silver. For thecomposite material of ceramics and metal, materials obtained byarbitrarily mixing both can be used. The particles have a diameter ofabout 0.1 to 10 μm, and preferably, are sintered particles.

The gas permeable substrate 1 of the present invention is characterizedin that the surface of the porous metallic plate, namely, any one of orboth of the upper and lower surfaces 3 a and 3 b are substantiallysmooth. Accordingly, the porous metallic plate 3 can be covered withanother thin film layer with good adhesion. Even if the pores 5 are notfilled with the particles until the surface of the porous metallic plate3 and the openings becomes flat, an arbitrary thin film layer can beformed on the surface. Specifically, since the porous metallic plate isreduced in thickness as described later, in some cases, the openings andthe surface of the metallic plate cannot be made completely flat in somecases by filling the pores with the particles. Therefore, in the gaspermeable substrate of the present invention, the surface thereof issomewhat uneven in some cases, but the surface is substantially smooth.Accordingly, the adhesion with another thin film layer is greatlyimproved compared to the conventional art. Moreover, since the surfaceof the metallic plate 3 is formed to be flat by filling the pores 5 withthe particles, an arbitrary thin film layer can be formed on the surfaceregardless of size of the pores 5.

For such a porous metallic plate 3, for example, sintered metal bodysuch as foam metal, a metal film with pores formed by chemical etching,and a metal film with pores formed by punching with a laser or electronbeam can be used. In the case where the porous metallic plate is thinand the shape or the openings thereof cannot be maintained, a frame isprovided on the outside thereof to support the porous metallic plate.Specifically, as shown in FIGS. 4A and 4B, when a frame 33 is providedin the periphery of the gas permeable substrate 1, gas permeablesubstrates 30 and 32 with improved mechanical strength and the pores 5maintained, can be obtained. For example, as shown in FIG. 10, when theporous metallic plate 3 is etched from the both sides, a shape suitablefor filling particles can be obtained.

For the materials constituting the porous metallic plate 3, stainlesssteel (SUS), Inconel, nickel, silver, platinum, copper, or arbitrarycombinations of these metals can be used. This enables the porousmetallic plate 3 to have electrical conductivity. It is preferable thatthe thickness of the porous metallic plate is within a range of 0.03 mmto 1 mm in the light of reduction in weight and thickness of a device.When the thickness is less than 0.03 mm, the strength is small, and whenthe thickness is more than 1 mm, the plate is thick and heavy, andtherefore, the gas permeable substrate cannot be made thin.

For the pore-forming material added to form the particle layer 7, amaterial which is decomposed by baking to make the particle layer porouscan be used, such as carbon and an organic material.

As described above, according to the present invention, the pores of theporous metallic plate are filled with particles, and the surface thereofis substantially smooth. Accordingly, it is possible to provide alightweight and thin gas permeable substrate which has high gasdiffusion and a high contact rate and adhesion with the functionalmaterial. Herein, the particle layer 7 is formed within the pores 5 andon the upper surface 3 a in FIG. 1. However, as shown in FIG. 2, the gaspermeable substrate of the present invention may be a gas permeablesubstrate 10 in which the particle layer 7 is provided in the pores 5and the upper and lower surfaces 3 a and 3 b of the porous metallicplate 3. This enables the strength of the gas permeable substrate to befurther increased. As shown in FIG. 3, the gas permeable substrate ofthe present invention may be a gas permeable substrate 20 in which theparticle layer 7 is provided only within the pores 5. Thus, a gaspermeable substrate formed into a thin film can be obtained. Moreover,as shown in FIG. 7, it is not necessary that all the pores 5 of theporous metallic plate 3 are filled with the particle layer 7, and everif the gas permeable substrate has the pores filled with particles tosome extent and has a smooth upper surface, the gas permeable substrateis within the technical scope of the present invention.

The gas permeable substrate 1 of the present invention is characterizedin that the surface of the porous metallic plate 3 is substantiallysmooth. However, this “substantially” is an expression made taking intoaccount various inevitable errors in a manufacturing process. The scopeincluding the inevitable errors also belongs to the technical scope ofthe present invention as long as a desired effect can be obtained.

Second Embodiment

Next, a detailed description will be given of a solid oxide fuel cell(SOFC) using the gas permeable substrate of the present invention. Asfor the construction of the solid oxide fuel cell of this embodiment,similar parts to those of the first embodiment are given the samenumerals in the drawings, and overlapping description will be omitted.

The SOFC of the present invention is constructed by using the gaspermeable substrate of the first embodiment. Specifically, the SOFC isconstructed by stacking single cells, each of which includes a powergenerating element stacked on the upper surface and/or the lower surfaceof the gas permeable substrate. Since the surface of the gas permeablesubstrate of the present invention is smooth, a thin and lightweightpower generating element can be formed on the entire gas permeablesubstrate, and an SOFC operating at low temperature can be obtained.Hereinafter, a detailed description will be given using FIGS. 5 and 6.The power generating element indicates a stacked body including a fuelelectrode, an electrolyte, and an air electrode, or intermediate layerswhen needed. The stacking is not limited to coupling the single cells inthe thickness direction thereof, and also involves the coupling in theplane direction.

As shown in FIG. 5, there is an SOFC 40 as the SOFC of the presentinvention, which includes an electrolyte layer 43, an intermediate layer44, and an air electrode layer 45 formed on a gas permeable substrate41. The gas permeable substrate 41 includes a fuel electrode layer 42formed on the porous metallic plate 3. Since the gas permeable substrate41 of the present invention has a smooth surface, the electrolyte layer43, the intermediate layer 44, and the air electrode layer 45 can beformed to be thin and uniform. Moreover, a fuel electrode material isused for the particle layer within the gas permeable substrate.Accordingly, reactivity between the diffused fuel gas (hydrogen gas,hydrocarbon gas, or the like) and oxygen ions is increased, and as aresult, the power generation efficiency can be increased.

The SOFC of the present invention can be an SOFC in which the pores ofthe porous metallic plate are filled with a reforming catalyst and anelectrode material and a stacking structure including two or more layersis formed in the pores. Herein, the electrode material is a conceptincluding a fuel electrode material constituting the fuel electrodelayer, an air electrode material constituting the air electrode layer,and an intermediate layer material constituting the intermediate layer.Specifically, as shown in FIG. 6, a gas permeable substrate 51 can beused in which a reforming catalyst layer 57 and a fuel electrode layer52 are provided within the pores 5 of the porous metallic plate 3. AnSOFC 50 of the present invention can be obtained by providing a firstintermediate layer 53, an electrolyte layer 54, a second intermediatelayer 55, and an air electrode layer 56 on the gas permeable substrate51. In the SOFC 50, since the reforming catalyst layer 57 and the fuelelectrode layer 52 are provided within the pores 5 of the porousmetallic plate 3, fuel gas can be supplied to the fuel electrode layer52 after flowing through the reforming catalyst layer 57 to be reformedso as to have a preferable gas composition. Moreover, since thereforming catalyst and the fuel electrode material are arranged withinthe porous metallic plate, the SOFC can be further reduced in thickness.

The SOFC 40 of the present invention has a structure in which theintermediate layer 44 is provided between the electrolyte layer 43 andthe air electrode layer 45. The SOFC 50 of the present invention has astructure in which the first intermediate layer 53 is provided betweenthe fuel electrode layer 52 and the electrolyte layer 54, and the secondintermediate layer 55 is provided between the electrolyte layer 54 andthe air electrode layer 56. Since the intermediate layer is providedbetween the fuel electrode layer and the electrolyte layer, the contactresistance between the fuel electrode layer and the electrolyte layercan be reduced. Moreover, since the intermediate layer is providedbetween the electrolyte layer and the air electrode layer, theresistance to ionization reaction of oxygen molecules can be reduced.Accordingly, ionization of oxygen molecules is promoted, and the powergeneration efficiency can be increased. It is preferable to provide theintermediate layers between the fuel electrode layer and the electrolytelayer and between the electrolyte layer and the air electrode layer, butit is possible to obtain the SOFC having high power generationefficiency without the intermediate layers. The most preferredembodiment is the SOFC shown in FIG. 5, namely, the SOPC 40, which isobtained by providing the fuel electrode layer 42 in the porous metallicplate 3 to form the gas permeable substrate 41 with the upper surfacemade smooth, and then stacking the electrolyte layer 43, theintermediate layer 44 and the air electrode layer 45. The SOFC 40 is themost preferred embodiment also from the viewpoint of reduction inthickness and weight.

In the SOFC 50 of the present invention, the pores 5 of the porousmetallic plate 3 are filled with the reforming catalyst layer 57 and thefuel electrode layer 52, but the present invention is not limited tothis. The pores may be filled with another electrode material to beformed into a two layer structure. Specifically, the fuel electrodelayer 52 and the first intermediate layer 53 can be provided within thepores 5. In the case of an SOFC not using the intermediate layer, thefuel electrode layer and the electrolyte layer may be provided withinthe pores. The fuel gas can be made suitable by providing the reformingcatalyst layer 57, but the reforming catalyst is not required to beprovided.

The power generating element and the reforming catalyst can be formed inthe gas permeable substrate by sputtering, deposition, aerosoldeposition, ion plating, ion clustering, laser beam ablation, spraythermal decomposition, or the like. Moreover, the power generatingelement and the reforming catalyst can be formed by sequentially usingany of these methods.

For the fuel electrode material, nickel, nickel cermet, Ni-yttriastabilized zirconia (YSZ) cermet, Ni-samaria doped ceria (SDC) cermet,platinum, and the like can be used. For the electrolyte layer material,stabilized zirconia can be used. For the air electrode material,lanthanum cobalt oxide (La_(1-x)Sr_(x)CoO₃, etc.), lanthanum manganeseoxide (La_(1-x)Sr_(x)MnO₃, etc.), and the like can be used. For thematerial of the reforming catalyst layer, transition metals can be usedsuch as platinum (Pt), palladium (Pd), cobalt (Co), rhodium (Rh), nickel(Ni), iridium (Ir), rhenium (Re), and group 8 transition metals can alsobe used such as ruthenium (Ru), and iron (Fe). Further, the material ofthe reforming catalyst layer can also be metal oxide such as aluminumoxide (Al₂O₃), magnesium oxide (MgO), chromium oxide (Cr₂O₃), siliconoxide (SiO₂), tungsten oxide (WO₂, WO₃, etc.), zirconium oxide (ZrO₂),cerium oxide (CeO₂), and bismuth oxide (Bi₂O₃). For the intermediatelayer material, samaria-doped ceria (SDC) and the like can be used.

In the SOFC using the gas permeable substrate of the present invention,the porous metallic plate 3 can serve as a collector since the porousmetallic plate 3 uses an electrical conductive material. Accordingly,when the gas permeable substrate of the present invention is used aspart of the SOFC, the electrode material can be used for the particlelayer, and the porous metallic plate can be used as the collector. Theelectrode material is supported by the collector, so that the gaspermeable substrate can be made thinner. Furthermore, since the contactarea between the electrode material and the collector is increased, theelectrical performance can be improved.

Moreover, since the surface of the gas permeable substrate of thepresent invention is smooth, it is possible to form a thin andlightweight power generating element on the entire substrate and obtainthe SOFC operating at low temperature. Moreover, since part of the powergenerating element, namely, electrode material is filled in thesubstrate, the contact area is increased, and an SOFC having goodstrength and gas diffusion is obtained.

In the SOFC 40 of FIG. 5, the air electrode layer 45, the intermediatelayer 44, the electrolyte layer 43, and the fuel electrode layer 42 areshown in this order beginning from the upper surface of the SOFC 40, butthe order thereof may be the fuel electrode layer 42, the electrolytelayer 43, the intermediate layer 44, and the air electrode layer 45beginning from the upper surface. Moreover, also in the SOFC 50 of FIG.6, the stacking order may be reversed.

Hereinafter, the present invention will be described in further detailusing examples, but the present invention is not limited to theseexamples.

EXAMPLE 1

As shown in FIG. 1, for the porous metallic plate 3, a plurality ofpores of φ=0.1 mm were provided by photo etching in an etching boardwhich was composed of SUS 304 and 0.1 mm thick. Subsequently, for theparticle layer 7, paste of the fuel electrode material which wascomposed of Ni—SDC and had a particle size of 2 μm was applied with athickness of 0.12 mm on the porous metallic plate 3 by screen printing,and then baked at 1050° C. in H₂ reducing atmosphere. In this manner,the gas permeable substrate shown in FIG. 1 was obtained. FIG. 10 showsan enlarged photograph of a section of this gas permeable substrate.

EXAMPLE 2

As shown in FIG. 2, for the porous metallic plate 3, foam metal whichwas composed of Pt and 1 mm thick and had a porosity of 98% was obtainedby sintering of metal powder. Subsequently, for the particle layer 7,paste of the fuel electrode material which was composed of Ni—YSZ andhad a particle size of 5 μm was applied with a thickness of 1.2 mm onthe porous metallic plate 3 by dipping, and then baked at 1050° C. in H₂reducing atmosphere. In this manner, the gas permeable substrate shownin FIG. 2 was obtained. FIG. 11 shows an enlarged photograph of asection of this gas permeable substrate.

EXAMPLE 3

As shown in FIG. 7, for the porous metallic plate 3, pores of φ=0.2 mmwere provided by laser processing in a punching board which is composedof Ni and 0.2 mm thick. Subsequently, for the fuel electrode layer, afuel electrode material which was composed of Ni—YSZ and has a particlesize of 2 μm was pressed and attached with a thickness of 0.15 mm on theporous metallic plate 3 by the green sheet method, and then baked at1050° C. in H₂ reducing atmosphere to obtain a gas permeable substrateprovided with the fuel electrode layer 42. Further, for the thin filmpower generating element, the obtained gas permeable substrate wascovered by screen printing with an electrolyte material which wascomposed of YSZ and has a particle size of 0.03 μm to form theelectrolyte layer 43. The obtained electrolyte layer 43 was covered withan air electrode material which was composed of SSC (Sm and Sr addedcobalt oxide) and had a particle size of 5 μm by screen printing with athickness of 10 μm to form the air electrode layer 45. In this manner,an SOFC cell 60 shown in FIG. 7 was obtained. In the SOFC cell 60, powergeneration of 0.1 W/cm² was confirmed.

EXAMPLE 4

As shown in FIG. 3, for the porous metallic plate 3, a plurality ofpores of φ=0.1 mm were provided by photo etching in an etching board,which is composed of SUS 304 and 0.1 mm thick. Subsequently, for theparticle layer 7, paste of the fuel electrode material which wascomposed of Ni and had a particle size of 10 μm was applied with athickness of 0.12 mm on the porous metallic plate 3 by screen printing,and then baked at 1050° C. in H₂ reducing atmosphere. In this manner,the gas permeable substrate 20 shown in FIG. 3 was obtained.

EXAMPLE 5

As shown in FIG. 8, for the porous metallic plate 3, a plurality ofpores of φ=0.1 mm were provided by photo etching in an etching board,which was composed of SUS 304 and 0.1 mm thick. Subsequently, paste ofthe fuel electrode material which was composed of Ni—SDC and had aparticle size of 2 μm was applied on the upper surface 3 a with athickness of 60 μm by screen printing to form the fuel electrode layer52. Furthermore, paste of the reforming catalyst layer material whichwas composed of Pt and had a particle size of 3 μm was applied on thelower surface 3 b with a thickness of 60 μm by screen printing, and thenbaked at 1050° C. in H₂ reducing atmosphere to form the reformingcatalyst layer 57. In this manner, the gas permeable substrate 70 shownin FIG. 8 was obtained.

COMPARATIVE EXAMPLE 1

As shown in FIG. 9, for a porous metallic plate 3′, metallic mesh, whichwas composed of SUS 304, 0.25 mm thick, and φ=0.1 mm, was obtained byplain Dutch weaving. Subsequently, for a particle layer 7′, paste of afuel electrode material which was composed of Ni—SDC and had a particlesize of 2 μm was applied on the obtained metallic mesh at a thickness of0.1 mm by screen printing, and then baked at 1050° C. in H₂ reducingatmosphere to obtain a gas permeable substrate as shown in FIG. 9.

In the examples 1 to 5, the gas permeable substrates which had goodadhesion between the substrate and the particles and were made thin wereobtained. Since there was the fuel electrode layer on the upper surfaceof the porous metallic plate and within the pores in each of the gaspermeable substrates of the examples 1 to 3 and 5, the gas was diffusedon the upper surface of the metallic plate and efficiently transferred.In the example 2, since the fuel electrode layers were on the upper andlower surfaces of the porous metallic plate, the stress from the upperand lower surfaces was well balanced, and the durability of thesubstrate was improved. In the example 3, the thin SOFC cell furtherincluding the power generating element on the gas permeable substratewas easily obtained. Furthermore, in the example 3, the fuel electrodematerial was pressed and attached by the green sheet method, which is aneasy manufacturing method, so that man-hours were reduced. In theexample 4, since the fuel electrode layer was formed within the pores,the adhesion between the fuel electrode layer and the substrate materialwas good. In the example 5, since the fuel electrode layer and thereforming catalyst layer were provided within the pores, it becamepossible to further reduce the thickness. On the contrary, in thecomparative example 1, since the metallic mesh is covered with the fuelelectrode layer, the fuel electrode layer was thickened. Moreover, it isinferred that the adhesion between the porous metallic plate and thefuel electrode layer was low since the contact area between the porousmetallic plate and the fuel electrode layer was small. Moreover, whenthe particle layer is made thin, it is impossible to obtain a smoothsurface because of the surface shape of the porous metallic plate 3′.

The entire content of a Japanese Patent Application No. P2002-375781with a filing date of Dec. 26, 2002 is herein incorporated by reference.

Although the invention has been described above by reference to certainembodiments of the invention, the invention is not limited to theembodiments described above will occur to these skilled in the art, inlight of the teachings. The scope of the invention is defined withreference to the following claims.

INDUSTRIAL APPLICABILITY

As explained above, according to the present invention, the pores of theporous metallic plate are filled with the particles and the surfacethereof is smoothed. Therefore, it is possible to provide a thin andlightweight gas permeable substrate which has high gas diffusion and hasa high contact rate and adhesion with the functional material, and toprovide a solid oxide fuel cell using the same.

1. A gas permeable substrate, comprising: a porous metallic plate havinga plurality of pores which form openings in an upper surface and/or alower surface thereof; and particles filled in the pores, wherein atleast one of the upper surface and the lower surface of the porousmetallic plate is substantially smooth.
 2. A gas permeable substrateaccording to claim 1, wherein not less than 30% of the upper surfaceand/or the lower surface of the porous metallic plate is covered withthe particles.
 3. A gas permeable substrate according to claim 1,wherein the particles are constituted by any one of ceramics and acomposite material of ceramics and metal.
 4. A gas permeable substrateaccording to claim 1, wherein the particles includes a reformingcatalyst and an electrode material, and a stacked structure having notless than two layers is formed within each of the pores.
 5. A gaspermeable substrate according to claim 4, wherein the electrode materialforms at least a layer selected from a group consisting of an airelectrode layer, a fuel electrode layer, and an intermediate layer.
 6. Agas permeable substrate according to claim 1, wherein the porousmetallic plate is any one of a sintered metal body, an etching board,and a punching board.
 7. A gas permeable substrate according to claim 1,wherein the porous metallic plate is a collector.
 8. A gas permeablesubstrate according to claim 1, wherein the porous metallic plateincludes at least one type of metal selected from a group consisting ofstainless steal, Inconel, nickel, silver, platinum, and copper.
 9. A gaspermeable substrate according to claim l, wherein a thickness of theporous metallic plate is within a range of 0.03 mm to 1 mm.
 10. A solidoxide fuel cell, comprising: a gas permeable substrate having a porousmetallic plate which includes a plurality of pores forming openings inan upper surface and/or a lower surface thereof; and particles filled inthe pores, wherein at least one of the upper and lower surfaces of theporous metallic plate are substantially smooth, and single cells arestacked, each single cell including power generating elements stacked onan upper surface and/or a lower surface of the gas permeable substrate.